The present invention relates to a method for making a dielectric material, in particular, a method for making a carbon doped oxide using an alkyl oxysilane precursor.
Semiconductor devices include metal layers that are insulated from each other by dielectric layers. As device features shrink, reducing the distance between the metal layers and between metal lines within each layer, capacitance increases. To address this problem, insulating materials that have a relatively low dielectric constant are being used in place of silicon dioxide (and other materials that have a relatively high dielectric constant) to form the dielectric layer that separates the metal lines.
A material that may be used to form such a low k dielectric layer is carbon doped oxide (xe2x80x9cCDOxe2x80x9d). Using this material instead of silicon dioxide to separate metal lines may yield a device having reduced propagation delay, cross-talk noise and power dissipation. In a conventional process for forming a CDO dielectric layer on a substrate (e.g., a silicon wafer), vapor phase species that provide a source or sources of silicon and carbon (xe2x80x9cprecursorsxe2x80x9d) and oxygen are introduced into a plasma enhanced chemical vapor deposition (xe2x80x9cPECVDxe2x80x9d) reactor. That reactor is then operated under conditions that cause a CDO layer to be deposited on the substrate. Example precursors used in such a PECVD process include alkyl silane and alkyl oxysilane precursors such as methyl silane, trimethyl silane, and dimethyl dimethoxysilane.
When, in such a process, the substrate temperature is maintained above 380xc2x0 C., the resulting CDO layer may have a dielectric constant of about 3.0. In some circumstances, it may be desirable to further reduce the dielectric constant for that layer. When an alkyl silane precursor (e.g., methyl silane or trimethyl silane) is used, maintaining the substrate temperature below 200xc2x0 C. during the deposition process may yield a CDO layer with a lower dielectric constant. Such materials, however, may exhibit unsatisfactory mechanical properties, such as edge flaking, due to poor adhesion and low cohesive strength. Materials deposited using an alkyl oxysilane precursor may have superior mechanical properties at equivalent dielectric constant.
Accordingly, there is a need for an improved process for making a carbon doped oxide. There is a need for such a process that generates a CDO material with a reduced dielectric constant and acceptable mechanical properties, which can be easily integrated into existing processes for making semiconductors. The method of the present invention provides such a process.